Numerous types of electrical power switching apparatus are known in the prior art. Different types of switching mechanisms are generally used within different voltage ranges. Within lower voltage ranges simple mechanical switches may prove suitable. In the higher voltage ranges, more complex and generally bulky switching mechanisms are required. Safety, reliability and space efficiency are important design criteria for the switching mechanisms utilized in the higher voltage ranges.
Within the medium voltage class, i.e. 2300-7200 volts, the typical switching mechanisms have generally been large. One reason for the large size of these prior art devices, has been the need to space the fuses a sufficient distance from the switching mechanism in order to protect the fuses from the arcing which usually occurs at the switching mechanism. Also, this type of prior art device has proven cumbersome to operate or repair because the fuses and the switches have been fixed together so that a large and sturdy roller system is required to move the fuses and the switches in unison.
In higher voltage ranges, for example 15,000 volts incoming voltage, other types of switching mechanisms, which are generally referred to as switchgear mechanisms are utilized. U.S. Pat. No. 2,885,501 to J. D. Wood et al; U.S. Pat. No. 2,914,635 to W. N. Lester et al; and U.S. Pat. No. 3,610,850 illustrate several switchgear mechanisms. In the above patents, rather large movable units carry fuses and other components into and out of a surrounding housing.
U.S. Pat. Nos. 3,530,418 and 3,579,045 to T. H. Keogh et al illustrate another type of high voltage switching mechanisms. In the Keogh et al patents, a switching mechanism is interposed between incoming high voltage lines and a step down transformer. The switching mechanism includes a circuit breaker connected to the incoming high voltage lines and a plurality of fuses interposed between the circuit breaker and a transformer which is disposed outside the switching mechanism. The fuses are mounted on a chassis mechanism which is slidable into and out of the housing of the switching mechanism.